Xerographic developing apparatus



1386- 1962 w. G. LEWIS El'AL XEROGRAPHIC DEVELOPING APPARATUS 5 Sheets-Sheet 1 Filed Dec. 23, 1960 INVENTORS. WILLIAM G. LEWIS Y JOHN w. WAGNER ATTORNEY Dec. 11, 1962 w. G. LEWIS ETAL XEROGRAPHIC DEVELOPING APPARATUS 5 Sheets-Sheet 2 Filed Dec. 23, 1960 INVENTORS.

A TTO R N EY WILLIAM G. LEWIS JOHN W. WAGNER BY Dec. 11, 1962 w. G. LEWIS EI'AL 3,067,720

XEROGRAPHIC DEVELOPING APPARATUS Filed Dec. 25, 1960 5 Sheets-Sheet 3 INVENTORS. WILLIAM G. LEWIS JOHN W. WAGNER A TTORN E Y FIG. 9

Dec. 11, 1962 w. G. LEWIS ETAL 3,067,720

XEROGRAPHIC DEVELOPING APPARATUS Filed Dec. 25, 1960 5 Sheets-Sheet 4 IN V EN TORS.

WILLIAM G. LEWIS JOHN W WAGNER ATTORNEY 5 Sheets-Sheet 5 ATTORNEY 8 5 R mw T E N Tm W A W u N m H ww kvw kvw/jo Dec. 11, 1962 w. G. LEWIS EI'AL XEROGRAPHIC' DEVELOPING APPARATUS Filed Dec. 23, 1.960

United States Patent Q 3,967,726 'XERQGRAIPHIC DEVELQiliN-G APPARATUS Wiiliam G. Lewis, Rochester, and Ziohn W. Wagner, Penfield, N.Y., assignor to Xerox Corporation, a corporation of New York Filed Dec. 23, 196i), No. 77,958 3 Clain (Cl. ltd-3G8) This invention relates to a developing apparatus for use in developing electrostatic latent images.

More specifically, the invention relates to improved automatic developing apparatus for use in an automatic xerographic reproducing apparatus.

In the process of xerography, for example, as disclosed in either Carlson Patent 2,297,691, issued October 6, 1942, or in Carlson Patent 2,357,809, issued September 12, 1944, a xerographic plate, comprising a layer of photo-conductive insulating material on a conductive backing, is given a uniform electric charge over its surface and is then exposed to the subject matter to be reproduced, usually by conventional projection techniques. This exposure discharged the plate areas in accordance with the radiation intensity which reaches them and thereby creates an electrostatic latent image on or in the plate coating.

Development of the image is effected with developer material or developers which comprise, in general, a mixture of a suitable pigmented or dyed electroscopic powder, hereinafter referred to as toner, and a granular carrier material, which latter functions to carry and to generate triboelectric charges on the toner. More exactly, the function of the granular material is to provide the me chanical control to the powder, or to carry the powder to an image surface and, simultaneously, to provide almost complete homogeneity of charge polarity. In the development of the image, the toner powder is brought into surface contact with the coating and is held thereon electrostatically in a pattern corresponding to the electrostatic latent image. Thereafter, the developed Xerographio image is usually transferred to a support or transfer material to which it may be fixed by any suitable means.

Development of the electrostatic latent images in commercial line-copying automatic xerographic machines is usually effected at a developing station of the machine wherein is located a developer housing having a lower or sump portion for accumulating developer material. Mounted within the developer housing is a bucket type conveyor continually in motion while the machine is in operation to carry the developer material from the sump to the upper portion of the developer housing from where the developer material is cascaded over a hopper chute onto the drum. This type of developing mechanism is well suited for use in automatic machines since continuous operation of the conveyor will efiect a continuous developing process.

In the course of operation of the developing process, the carrier material is not depleted, but the toner is of course continuously attracted to the electrostatic latent image to effect its development and then transferred to a support material. Toner thus consumed must be replenished if proper development of the electrostatic images is to be maintained, as is desired in an automatic machine.

As previously described, the toner may be a suitably pigmented or dyed electroscopic powder, and although a black pigmented powder is usually used to develop the electrostatic latent images, other colored toners may be used to develop the images. When it is desired to change from say a black toner to a blue-tinted toner, it is apparent that blue toner cannot be added to the black toner Without affecting the resultant color of the combination of toners. Thus, if it is desired to use blue toner, for example, the blue toner must be mixed with a clean supply of granular carrier material.

3,667,?2h Fatented Dee. ll, 1962 To use this new batch of developer material containing the blue toner, it would either be necessary to empty the developer mixer containing the black toner from the developer housing and replace it with this new mixture or to deposit the new mixture in a separate developer assembly which could be attached to the machine in place of the original developer assembly.

It is therefore the principal object of this invention to improve developing apparatus whereby the conveyor assembly, toner dispenser, and their drives are formed as an integral component readily mounted on a xerographic apparatus.

Another object of the invention is to improve xerographi developing apparatus containing a toner dispenser mounted therein which is operated at a speed in direct relationship to the rate of operation of the conveyor mechanism of the developing apparatus whereby toner is added to the developing mixture at an optimum rate directly dependent on the speed at which the developing material is cascaded onto a xerographic drum for developing.

For a better understanding of the invention as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic illustration of a preferred form of an automatic xerographic reproducing apparatus using a developing apparatus constructed in accordance with the invention;

FIG. 2 is a left-hand view of the xerographic reproducing apparatus of FIG. 1 illustrating the mounting position of a developing apparatus constructed in accordance with the invention;

PEG. 3 is a perspective view of the developing apparatus of the invention removed from the apparatus to show details of its construction;

FIG. 4 is a sectional view of the developing apparatus taken along line 44- of FIG. 2;

FIG. 5 is a top view of a preferred form of toner dispenser for use in the developing apparatus but removed from the apparatus to show details of its construction;

PEG. 6 is an end view of the toner dispenser;

PEG. 7 is a sectional view of the toner dispenser taken along line 77 of FIG. 5;

FIG. 8 is an enlarged sectional view showing the details of the toner outlet of the dispenser only;

FIG. 9 is a top enlarged view of the dispenser drive mechanism; and

FIG. 10 is an enlarged sectional view taken along line ltl-1ti of FIG. 9.

General As shown, the xerographic apparatus comprises a xerographic plate including a photoconductive layer or lightreceiving surface on a conductive backing and formed in the shape of a drum, generally designated by numeral 20, which is journaled in a frame, including frame plates 10 and 11 suitably connected together and maintained rigidly in spaced relation to each other, to rotate in the direction indicated by the arrow to cause the drum surface sequentially to pass a plurality of xerographic processing stations.

For the purpose of the present disclosure, the several xerographic processing stations in the path of movement of the drum surface may be described functionally as follows:

A charging station, at which a uniform electrostatic charge is deposited on the photoconductive layer of the xerographic drum;

An exposure station, at which a light or radition pattern of copy to be reproduced is projected onto the drum surface to dissipate the drum charge in the exposed areas thereof and thereby form a latent electrostatic image of the copy to be reproduced;

A developing station, at which a xerographic developing material including toner particles having an electrostatic charge opposite to that of the electrostatic latent image are cascade over the drum surface, whereby the toner particles adhere to the electrostatic latent image to from a xerographic powder image in the configuration of the copy of the reproduced;

A transfer station, at which the xerographic powder image is electrostatically transferred from the drum surface to a transfer material or support surface; and

A drum cleaning and discharge station, at which the drum surface is first charged and then brushed to remove residual toner particles remaining thereon after image transfer, and at which the drum surface is exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

The charging station is preferably located as indicated by reference character A in the schematic illustration of the apparatus. In general, the charging apparatus or corona charging device 21 includes a corona discharge array of one or more discharge electrodes that extend transversely across the drum surface and are energized from a high potential source and are substantially enclosed within a shielding member.

Next subsequent thereto in the path of motion of the xerographic drum is an exposure station E. This exposure station may be one of a number of types of mechanisms or members such as desirably an optical scanning or projection system or the like designed to project a line copy image onto the surface of the photoconductive xerographic drum from a suitable original.

The optical scanning or projection assembly consists of a copyboard in the shape of a drum, hereinafter referred to as copy drum 22, which is adapted to support copy to be reproduced and arranged to rotate in lightprojection relation to the moving light-receiving surface of the xerographic plate. Uniform lighting is provided by suitable lamps attached to a slotted light reflector 23 mounted adjacent to the copy drum.

A light shield 24 adapted to protect the xerographic plate from extraneous light is positioned adjacent to the surface of the xerographic plate. A slot aperture 25 in the light shield extends transversely to the path of movement of the light-receiving surface of the xerographic drum 2%) to permit reflected rays from the copy drum to be directed against a limited transverse area of the light-receiving surface as it passes therebeneath.

To enable the optical system to be enclosed within a relatively small cabinet, a folded optical system including an object mirror 26, a lens 27, and an image mirror 23 is used in the preferred embodiment of the apparatus.

Copy fed through paper guides 31 to the copy drum is removably secured thereon by a suitable gripper mechanism for movement therewith in timed relation to the movement of the xerographic drum whereby a flowing image of the copy is projected onto the xerographic drum. The copy is held against the surface of the copy drum by means of guides 32 and 33, the latter also preventing the trailing edge of the copy from contacting the web cleaner 54. After the copy is scanned it can be released from the copy drum to be transported out of the machine by copy feed out roller 34 coacting with the peripheral surface of the copy drum to forward the copy through copy guide 30.

Adjacent to the exposure station is a developing station C in which there is positioned a developer apparatus 35 including a developer housing having a lower or sump portion for accumulating developer material 36. Mounted within the developer housing is a motor driven buckettype conveyor used to carry the developer material previously supplied to the developer housing to the upper 4 portion of the developer housing from where the developer material is cascaded over a hopper chute onto the drum.

As the developer material cascades over the drum, toner particles of the developer material adhere electrostatically to the previously formed electrostatic latent image areas on the drum to form a visible xerographic powder image; the remaining developer material falling off the peripheral surface of the drum into the bottom of the developer housing. Toner particles consumed during the developing operation to form the xerographic powder images are replenished by a toner dispenser 37, of the type disclosed in copending application Serial No. 77,955, filed concurrently herewith on December 23, 1960, in the name of Roger H. Eichorn and William G. Lewis, mounted within the developer housing.

Positioned next adjacent to the developing station is the image transfer station D which includes suitable sheet feeding mechanism adapted to feed sheets of paper successively to the xerographic drum in coordination with the presentation of the developed image on the drum at the transfer station. The sheet feeding mechanism includes a sheet source such as tray 41 for a plurality of sheets of a suitable support material, that is, sheets of paper or the like, a separator roller 42 adapted to feed the top sheet of the stack of support material to a sheet conveyor mechanism 43 having paper grippers 44 thereon which carry the sheet support material into contact with the rotating xerographic drum in coordination with the appearance of a developed image at the transfer station.

The transfer of the xerographic powder image from the drum surface to the support material is effected by means of a corona transfer device 45 that is located at or immediately after the point of contact between the support material and the rotating xerographic drum. The corona transfer device 45 is substantially similar to the corona discharge device that is employed at the charging station in that it also includes an array of one or more corona discharge electrodes that are energized from a suitable high potential source and extend transversely across the drum surface and are substantially enclosed with a shielding member. In operation, the electrostatic field created by the corona transfer device is effective to tack the transfer material electrostatically to the drum surface and simultaneously with the tacking action, the electrostatic field is effective to attract the toner particles comprising the xerographic powder image from the drum surface and cause them to adhere electrostatically to the surface of the support material.

As the paper gripper mechanism continues to move for ward in its closed circuit, it will strip the support material from the xerographic drum and carry it to a fixing device, such as, for example, heat fuser 46, whereat the developed and transferred xerographic powder image on the support material is permanently fixed thereto.

After fusing, the finished copy is preferably discharged from the apparatus at a suitable point for collection externally of the apparatus. To accomplish this there is provided a pair of delivery rolls 47 and 48 by means of which the copy is delivered to a copy holder after it is released by the gripper mechanism. Suitable cam means are provided at the receiving and delivery stations of the conveyor mechanism to actuate the paper gripper at these stations to receive or discharge a sheet of support material.

The next and final station in the device is a drum cleaning station E whereat any powder remaining on the xerographic drum after the transfer step is removed and. whereat the xerographic drum is flooded with light to cause dissipation of any residual electrical charge remain, ing on the xerographic drum.

To aid in the removal of any residual powder remain ing on th xerographic drum there is provided a corona precleaning device 51 that is substantially similar to the corona discharge device that is employed at charging station A. Removal of residual powder from the Xero-.

graphic drum is effected by means of a web cleaner device 54 adapted to continuously feed a clean fibrous web material into wiping contact with the xerographic drum. As shown, the web material 55 is taken from a supply roll 56 and transported around a cleaning roll 57, preferably made of rubber, around a guide plate 58 to be wound on a take-up or rewind roll 61.

Any residual electrical charge remaining on the xerographic drum is dissipated by light from a fluorescent lamp 62 mounted in a suitable bracket above the xerographic drum, a suitable starter being provided for energizing the fluorescent lamp.

Suitable drive means drive the xerographic drum, the copy drum, and the sheet conveyor mechanism at predetermined speeds relative to each other, and to effect operation of the paper separator roll, and the web cleaner mechanism, the latter being driven at a speed whereby relative movement between the Xerographic drum and the web material is effected. Suitable drive means are also provided for effecting operation of the conveyor mechanism and toner dispenser of the developing apparatus assembly, as described hereinafter.

It is believed that the foregoing description is sufficient for the purposes of this application to show the general operation of a xerographic reproducing apparatus. For further details concerning the specific construction of the Xerographic apparatus shown, reference is made to copending application, Serial No. 77,954, filed concurrently herewith on December 23, 1960, in the name of Roger H. Eichorn and William G. Lewis.

Development System Referring now to the subject matter of the invention there is shown in FIGS. 2 to 11, inclusive, a preferred form of developing apparatus constructed in accordance with the invention.

In order to effect development of the electrostatic latent image on the cylindrical xerographic plate, the developing system shown, includes a developer apparatus which coacts with the cylindrical xerographic plate or drum to form a development zone wherein the charged and exposed surface of the drum is developed to form a powder image of the copy.

For this purpose a developer housing is mounted ad- 'jacent to the xerographic drum to form the development zone. Mounted within the developer housing is a driven bucket-type conveyor used to carry the developer material previously supplied to the developer housing to the upper portion of the developer housing from where the developer material is cascaded over a hopper chute onto the drum. As the developer material cascades over the drum, toner particles of the developer material adhere electrostatically to the previously formed electrostatic latent image areas on the drum, the remaining developer material falling off the peripheral surface of the drum into the bottom of the developer housing. Toner particles consumed during the development operation to form the visible powder images are replenished by a toner dispenser 37 mounted within the developer housing.

Specifically, the developer assembly or apparatus 35 includes a box-like developer housing having side walls 291 and 2%; and a sheet metal outer shell or cover forming in the lower portion thereof a reservoir for developer material 36, these elements being held together, with seals 2% interposed therebetween, by tie rods 2% to form a unitary structure. As shown, the side walls are formed with a concave edge portion in conformity with the shape of a Xerographic plate to permit the developer housing to be positioned closely adjacent to the xerographic drum. Seals 2% are secured, as by fasteners 2ft? to the concave edge portions of the side walls to contact the outer edges of the xerographic drum to form a powder tight seal between the developer assembly and the xerographic drum.

A suitable bucket-type conveyor is used to convey developer material from the reservoir portion of the developer housing to the upper portion of the developer housing from where it is cascaded over the xerographic drum. In the embodiment disclosed the bucket-type conveyor consists of a series of parallel spaced buckets 207 secured as by staples or rivets to a pair of endless conveyor belts wrapped around conveyor pulleys 211, having pins 21 thereon to engage the lugs of the conveyor belts, secured to the drive and idler shafts 213- and 214, respectively, to rotate therewith, the shafts being journaled in hearings 215.

Each hearing is mounted in a cup-shaped bearing housing 216, one end of the bearing butting against a seal 2 17 and the other end butting against socket plate 218, each socket plate and bearing housing assembly being secured by means of screws 219 to the side walls of the developer housing. Suitable thrust washers 221 encircle the shafts between each pulley and the bearing housing adjacent thereto.

The conveyor is actuated by means of gear 222 secured to drive shaft 213, outboard of the developer housing, which meshes with gear 223 secured to the shaft of gear head motor MST-4 mounted on spacers 224 secured to the side walls 2&2.

To deflect the developing material and to spread this material across the face of the drum as the developing iaterial is emptied out of the conveyor buckets by gravity, a hopper chute 225 is secured to the side walls of the developer housing. As the Xerographic drum rotates, developing material previously tumbled over the flanged hopper chute onto the drum will cascade over the drum and eventually fall off or be thrown off to the surface or the xerographic drum to fall into the reservoir portion of the developer housing, a pick-off chute 226 being secured to the side walls in position to overlie the bottom of the housing whereby developer material is directed to the reservoir portion of the developer housing.

For removably supporting the developer assembly in operative position adjacent to the xerographic drum the lower end extensions of the side plates are formed with a notched portions 223 whereby the assembly is sup-ported on rod 231 extending between plates 10 and 11 and secured thereto. By this arrangement the assembly can be pivoted around rod 231 either toward the Xerographic rum to place it in operative relation thereto, or it can be pivoted away from the drum to permit either servicing of the assembly or removal of the assembly from the machine.

To maintain the developer assembly in operative position adjacent to the xerographic drum, the side walls are provided with outwardly extending brackets 223 adapted to receive screws 232 by means of which the assembly is adjustably and removably secured to the back edges of plate 10 and to bracket 233 on plate 11,

As shown, each of the upper screws 232 is threaded through the brackets 229 to abut against plate 10 or bracket 233, whereas the bottom screws 232 extend through suitable apertures in brackets and are threaded into plate 1% or bracket 233 to hold the assembly in position.

As the developing mixture is cascaded over the xerographic drum, toner particles are eleotrostatically pulled away from the carrier component of the developer material and deposited on the drum to form xerographic powder images, while the partially denuded carrier par ticles pass off the drum into the reservoir. As toner powder images are formed, additional toner particles must be supplied to the developing mixture in proportion to the amount of toner deposited on the drum. To supply additional toner particles to the developer mixture, a toner dispenser is used to accurately meter toner to the developer mixture and is mounted in the developer housing through a suitable opening formed in the top, back portion of the outer shell.

Although any one of a number of well known powder or granulated material dispensers may be used, the toner dispenser shown is of the type disclosed in the referenced copending application, Serial No. 77,955, filed concurrently herewith on December '23, 1960.

Referring now in particular to the figures which illustrate a preferred embodiment of the toner dispenser 37, the toner dispenser includes a container for toner formed as a box having a top plate 241 to which is secured as by spot welding, two depending end plates 242 having a lower convex shaped portion, and cut-out portions centrally located therein, a depending left-hand bearing plate 243 and an enclosure or base plate 244 formed to match the contour of the end plates. The container is closed at one end by dust cap 245 and at its other end by righthand bearing plate 246 and the elements attached thereto as described in greater detail hereinafter.

The container is supported by means of the top plate 241 adapted to extend beyond the cut-out portion of the outer shell to rest on the top portion of the outer shell of the developer housing, with a suitable gasket or seal 247 sandwiched therebetween, the container being held in position by screws 232 passing through the top plates and threaded into the outer shell of the developer housing.

The top plate is provided with an inlet opening 243 through which toner may be deposited within the container, the inlet opening being closable by means of cover 251 pivotally secured by hinge 252 to the plate, the hinge being secured at one end of the cover plate and at its other end to the top plate. A gasket 253 encircles the outer edges of the cover in position to contact the top plate, so that, when the cover is closed the gasket is pressed against the top plate by means of the spring clips 227 pivotally secured to the outer shell of the developer housing.

Toner placed in the container is dispensed through apertures 254 in the lower portion of the base plate by means of cylindrical brush 255 secured to the threaded portion of drive shaft 256 journaled in bearings 257 and 257A mounted in bearing housings 258 and 258A secured to the right-hand bearing plate 246 and the lefthand bearing plate 243. The brush is secured axially against the shoulder of the drive shaft 256 by means of retaining ring 259 positioned in a suitable groove provided in the drive shaft.

A beater shaft 261 carrying a wire beater arm 262 secured thereto is journaled in bearings 263 and 263A mounted in bearing housings 264 and 264A and driven by gear 265 attached thereto which meshes with gear 266 on shaft 256. Axial alignment of the beater shaft is maintained at one end by hearing housing cover 271 mounted on the bearing housing 264A secured to the right-hand bearing plate, and at its other end by screw 272 threaded through dust cap 245 and secured by lock nut 273.

The bearing housings 258, 258A, 264 and 264A inserted through apertures formed in the bearing plates, are secured to their respective bearing plates as by peening over the edges of the bearing housing. Dust seals 267 and 268 encircle shafts 256 and 261, respectively, within the bearing housings to protect the bearings mounted therein from the toner particles.

The toner dispenser when mounted in the developer housing is driven by an extension shaft 274 inserted through a suitable aperture in the side wall 252 of the developer housing to engage the threaded or right-hand end of shaft 256, the washer seal 269 butting against the inside surface of the side wall around the aperture therein. The extension shaft carries a control lever 2'75 rotatably mounted thereon, a ratchet wheel 276 fixed by pin 277 thereon, and one end of guide lever 278 rotatably mounted thereon by means of bearing bushing 279 held in place by retaining ring 231 positioned in a suitable groove formed on the end of the extension shaft.

The ratchet wheel is moved by means of actuating arm or pawl 282 having a bearing 283 mounted thereon by means of which the actuating arm or pawl is journaled on bushing 284 encircling stud 285 secured to the guide lever. The actuating arm or pawl is biased into driving engagement with the ratchet wheel by a torsion spring 286 secured at one end to the actuating arm or pawl 232 and at its other end to the guide lever 273.

To effect movement of the actuating arm or pawl 282 to index the ratchet wheel 276, the guide lever 273 is slotted as at 237 to slidably receive drive pin 288 of the crank arm 229 secured to gear 222 mounted on drive shaft 213 of the developer conveyor, whereby the toner dispenser is operated at a rate dependent on the speed at which the developer conveyor is operated.

To vary the dispensing rate of the toner dispenser, which is dependent on the number of revolutions of the brush per unit of time, the number of revolutions of the brush per unit of time must be varied This may be done by varying the speed of the developer conveyor or with a fixed rate of speed for the developer conveyor the toner dispensing rate may be varied by varying the degrees through which the ratchet wheel is indexed by the actuating arm or pawl. in the embodiment shown the length of throw of the actuating arm or pawl 282 per cycle is adjusted by means of control lever 275.

Control lever 275 is provided with a cam portion 291 which can be variably positioned to interfere with the actuating arm or pawl to disengage it from the ratchet wheel after a predetermined length of travel.

To secure the control lever in a predetermined position, as determined by the operator, while still permitting the operator to move the control lever to a different setting movement, there is provided an adjustment plate 292 with scale serrations thereon by means of which the control lever may be indexed at a predetermined position. To force the control lever into frictional engagement with the adjustment plate 292 there is provided a friction plate 2'93 secured along with the adjustment plate to the side wall 202 of the developer housing by means of cap screws 294 threaded into the side wall, the friction plate being biased toward the control lever and the adjustment plate by springs 295 encircling the cap screws between the friction plate and the washer 296 butting against the head of the cap screws.

While the invention has been described with reference to the structures disclosed herein, it is not to be confined to the specific details set forth, as, for example, it is apparent that other types or forms of toner dispenser can be substituted for the toner dispenser disclosed herein. Other modifications or changes may readily become ap parent to those skilled in the art, and therefore this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.

What is claimed is:

l. A unitary developing apparatus for use in a xerographic reproducing apparatus wherein a xerographic plate in the shape of a drum is journaled for rotation in a frame element of the apparatus, the developing apparatus including a casing having a lower sump portion for accumulating developing material consisting of a mixture of toner powder and granular carrier material, and side walls formed with a concave edge portion in conformity with the shape of said xerographic plate; a bucket type conveyor mounted within said casing to carry developing material to the upper portion of said casing where it is cascaded onto said xerographic plate, drive means connected to said bucket-type conveyor for operating said bucket-type conveyor at a fixed speed, a toner dispenser mounted within said casing for depositing a metered quantity of toner powder to said lower sump portion, said drive means including means connected to said toner dispenser for operating said toner dispenser at varying speeds directly related to the speed of operation of said bucket-type conveyor, and said side walls including means adapted to coact with said frame element whereby said casing is manually movable from a first position where said casing is in an inoperative relation to said xerographic plate to a second position where said casing is in operative relation to said xerographic plate.

2. A developing apparatus for use in a xerographic reproducing apparatus wherein a xerographic plate in the shape of a drum is journaled for rotation, the developing apparatus including a casing having a lower sump portion for accumulating developing material consisting of a mixture of toner powder and carrier material, and side walls formed with a concave edge portion in conformity with said xerographic plate; a bucket-type conveyor mounted within said casing to carry developing material to the upper portion of said casing for cascading onto a xerographic plate, drive means connected to said bucket-type conveyor for operating said bucket-type conveyor at a predetermined speed, a toner dispenser mounted within said casing for dispensing a metered quantity of toner powder to said lower sump portion, a shaft journaled in one of said side walls and operatively connected to said toner dispenser for actuating said toner dispenser, a rachet fixed to one end of said shaft, a crank arm having a pin eccentrically mounted thereon and operatively connected to said drive means, a guide lever pivotably connected at one end to said shaft and at its other end provided with a slot to receive said pin, a pawl pivotably connected to said guide lever, a spring means connected at one end to said guide lever and at its opposite end to said pawl to normally bias said pawl into engagement with said rachet, and a control lever adjustably positioned to engage and arrest the movement of said pawl whereby the stroke of said pawl may be varied.

3. A developing apparatus for use in a xerographic reproducing apparatus wherein a Xerographic plate in the shape of a drum is journaled for rotation, the developing apparatus including a casing having a lower sump portion for accumulating developing material consisting af a mixture of toner powder and carrier material, and side walls formed with a concave edge portion in conforming with a Xerographic plate, a bucket-type conveyor mounted within said casing to carry said developing material to the upper portion of said casing for cascading onto said xerographic plate, drive means connected to said buckettype conveyor for operating said bucket-type conveyor at a pre-determined speed, a toner dispenser mounted on said casing for dispensing a quantity of toner powder into said casing, a shaft journaled in one of said side walls and operatively connected at one end to said toner dispenser for actuating said toner dispenser, a rachet wheel fixed to one end of said shaft, a guide lever pivotally connected at one end to said shaft and adapted to engage said drive means whereby said guide lever is pivoted about said shaft, a pawl pivotably connected to said guide lever, spring means operatively connected to said pawl to normally bias said pawl into engagement with said rachet wheel, a control lever pivotably connected to said shaft, said control lever having a cam portion thereon adapted to said pawl to limit the length of travel of said pawl, and means operatively connected to said control lever whereby said cam portion of said control lever is adjustably positioned to vary the length of travel of said pawl.

References Cited in the file of this patent UNITED STATES PATENTS 

